Selection of control valve actuator

For cut-off valves, ball valves or butterfly valves are generally used; for angular stroke types, cylinder actuators are more commonly selected； There is also the issue of thrust and stroke. Generally, a cylinder is chosen as a whole, and then, depending on the torque required, a gear-rack or fork-type cylinder actuator is selected.

This post was last edited by sdlyml on 2020-3-25 at 15:09. Diaphragm-type cut-off valves are also available. For example, pneumatic diaphragm bellows cut-off valves used for liquid chlorine. The main issue to consider is still the amount of leakage. Generally, for Class V seals, it is sufficient for liquids, while for gases it is Class VI. But hard seals are generally grade IV, such as in control valves. Bellows seals of grade V are also available; I’ve heard that grades VI are possible as well, though they might be more expensive – I’m not sure about that.

I checked the instrumentation selection specifications; for on/off valves with control valve actuators that require fast operation, cylinder-type actuators are recommended, and single-acting cylinders with spring return are preferred. The specifications do not state that this is not allowed. But for natural gas media, it’s only said to be useful; most of them are still of the cylinder type.

Except for a very small number of valves that have requirements regarding switching time, there is generally no specific specification for the actuator. Valves such as steam turbine quick-close valves have specific requirements regarding the time it takes to shut off the steam, which is why they are specially designed; however, these quick-close valves operate with direct hydraulic action. . . .

That’s right. Thank you for your guidance; I’ve learned a lot from it

A lot of knowledge can be learned here

For shut-off valves (on/off valves), the main consideration is the leakage rate, that is, the sealing grade. For conventional on-off valves, butterfly valves, gate valves, ball valves, and gate valves are used. Once the type of valve is determined, an appropriate actuator is selected; in principle, these on-off valves all use cylinder actuators. The main function of a shut-off valve is to cut off flow, not to regulate it. These valves can achieve a leakage rating of VI. Conversely, membrane actuators are primarily used in GLOBE control valves, and their main function is regulation rather than shut-off. Of course, there are also those that use cylinder actuators for adjustment. There are also shut-off-type thin-film control valves, but they are very rare; they are generally used in applications where high requirements are not placed on leakage levels. GLOBE control valves are generally of class IV, but they can also be achieved at class V. There are also film actuators equipped with butterfly valves and ball valves, but these are quite rare. So, choose a shut-off valve; prioritize the valve type first, and then select the actuator. Hope this helps!